1. Field of the Invention.
This invention pertains to a method of and an apparatus for dispensing beverage into an open receptacle with automatic dispensing shut-off in response to an electrical sensing of the level of dispensed beverage in the receptacle with an electrically conductive probe.
2. Description of Prior Art.
Dispensing of cold carbonated soft drinks is well known and has been witnessed by virtually every person in the United States. In the original mode of fountain dispensing, a "soda jerk" held a glass in one hand and manipulated a dispensing lever in the other hand and visually ascertained when the glass was full and then manually shut-off the dispenser. The next level of sophistication in dispensing, which was done primarily to increase the speed of dispensing and the productivity of counter workers, was to provide an actuator lever under the dispenser. The counter worker could then hold a glass in each hand, hold both glasses--one each against a respective dispensing valve actuator lever --and fill two glasses at a time.
Another method and structure provided to increase productivity was a timer-controlled dispenser. The original version of this device is the coin-operated cup-filling vending machine. The fountain dispensing adaptation of this is commonly referred to in the beverage dispensing industry as a "portion control". A typical portion control, as it is presently offered by several manufacturers and used by most fountain retailers, is an add-on electronic control having four push buttons and three adjustable timers. Three of the buttons provide small, medium and large portions via the three timers respectively. Each timer is adjustable to give a dispensing period of a user-set predetermined time. The fourth button is an overriding stop button. These portion controls are commonly seen today in theatres and fast food retail outlets. These portion controls were the state-of-the-art in carbonated beverage dispensing until the commercial success of the device of L. M. McIntosh U.S. Pat. No. 3,916,963 which will be hereinafter discussed.
The dispensing of carbonated soft drinks is not quite as easy as filling a glass with water or pouring a cup of coffee; it is much more complex and prone to adverse spurious events. Water, coffee, and other non-carbonated beverages do not foam and for the most part flow at predictable and pre-set rates. What you see in a glass or cup is what you have. The top level of the dispensed water or coffee is just that, it is the actual top level. Ice is not used with hot coffee and other hot beverages. The dispensing of hot water and hot non-carbonated beverages can be acceptably controlled and portioned with a timer together with some type of volumetric flow rate control.
Carbonated beverages are a different and relatively difficult fluid to dispense and to control. Carbonated beverages are almost always cooled down to about 32.degree. to 38.degree. F. (0.degree. to 2.degree. C.) and propelled by carbon dioxide gas. There are two basic types of carbonated beverage. Each type of beverage requires a specific type of dispensing valve. The first and now most-commonly seen type of carbonated beverage is "post-mix", wherein discrete supplies of syrup and carbonated water are supplied to a beverage dispensing head and are discretely valved and then combined together in a nozzle to form the complete beverage during flow into a beverage receptacle. Post-mix is now the preferred mode of soft drink dispensing in theatres and fast food retailers. The second type of carbonated beverage is "pre-mix", wherein a complete beverage is provided in a bulk vessel to the retailer. As an example, beer and wine are distributed and dispensed like this, as is pre-mix soft drink. Pre-mix soft drink is typically used where local water is of poor quality, or not available.
Carbonated beverage is difficult to handle because of the many variables and unexpected aberrations that occur. These include variations in the amount of ice, decarbonation and foaming, flow rate variations and beverage ratio variations. Customers will come in and unpredictably ask for "no ice", "some ice", "lots of ice", or "full of ice". Each counter person has a different standard of measure to satisfy each of these requests. Portion controls cannot compensate or consider whether or not there is ice in a cup. In addition, ice temperature influences volumetric efficiency of the beverage fill. If the ice has been warmed up to 32.degree. F. (0.degree. C.) and is not sub-cooled and has rounded edges, chilled carbonated beverage poured upon it will usually not foam. If the ice is sub-cooled, the carbonated beverage will foam and then collapse. Volumetric fills of only 25% are common when carbonated beverage is poured over sub-cooled ice. This phenomenon is commonly seen domestically when soft drinks are poured on ice cubes. It is irritating at home; and it is economically unviable in retailing. Portion controls cannot compensate for this phenomenon.
Decarbonation during dispensing is a phenomenon which can be caused by ice as just explained, but which is usually caused by something else. Decarbonated soft drink or beer is commonly called "foam", and is seen on top of beer and soft drinks. It sometimes is desirable on beer and is referred to as the "head". It is objectionable on soft drinks and causes a short fill. The U.S. consumer generally prefers a full glass of beer rather than 3/4 fill and 1/4 head. The European customer, in contrast, generally prefers a head. Decarbonation and foaming can be caused by turbulent flow in the dispensing head or nozzle, loss of or consumption of cooling capacity, over-carbonation, subcooling of beverage, too warm beverage, dirty or contaminated dispensing heads, dispensing valves which are only partially open, incorrect flow rates, bad water, dirty glasses, positioning the receptacle incorrectly, particulate in either syrup or water, and many other unpredictable causes.
Different beverages have different foaming characteristics. For example, low carbonated orange beverages seldom foam. Lemon-lime beverages seldom foam. Colas foam and are a problem. Root beer is a notorious foamer. Dietetic colas, which are also notorious foamers, are becoming the most popular new beverage in the 1980's.
Volumetric flow rates and beverage ratios delivered by carbonated beverage dispensers tend to change unpredictably over time. As ambient conditions, cooling capacities, propellant pressures, flow control obstruction, and draw rates vary between slack times and peak draw periods (i.e. lunch and evening meal times), the flow rates of beverage change. The standard nominal flow rate has been 1.5 ounces per second. This can easily and unpredictably vary between 1.0 and 2.0 ounces/second over the course of a day.
Portion controls have not been able to compensate for decarbonation, foaming, ice variation, and varying flow rates. Portion controls will work if everything is perfect and repetitively identical. Reality is seldom so idyllic.
The next effort to improve serving speed and productivity is to increase flow rates. Whereas the standard flow rate remains at 1.5 ounces/second, "high-flow" is now 2.5 ounces/second and experimental dispensing systems are attaining 5 ounces/second. These higher flow rates aggravate and multiply the previously explained problems and further require much faster re-active controls.
While these efforts at increased output and efficiency have been undertaken, a parallel line of effort has been made at devising an automatic dispensing shut-off control sysem that is responsive to the actual level of dispensed beverage in the receptacle, rather than time, flow rate, cup size or other merely secondary criteria. The physical level of dispensed beverage with respect to the upper rim of the beverage receptacle, is the primary criterion to determine a proper fill and portion of beverage.
One particularly advantageous approach for providing automatic shut-off uses an electrically conductive probe assembly for sensing dispensed beverage level. Examples of early attempts at this type of automatic shut-off control are shown in the Karlen U.S. Pat. No. 2,639,078, the Haynes U.S. Pat. No. 3,670,765 and the Nickerson U.S. Pat. No. 3,839,645.
In the McIntosh U.S. Pat. No. 3,916,963, use of an electrically conductive probe for sensing level of dispensed carbonated beverage was combined with an actuator lever. This provides a simple and effective way of both starting the dispensing (by mechanical movement of the probe/actuator lever) and stopping dispensing (by electrical contact of the liquid/foam beverage with the probe). Other later examples of the type of carbonated beverage dispenser control first proposed by McIntosh are shown in the Reichenberger U.S. Pat. No. 4,236,553, the Bennett U.S. Pat. No. 4,641,692, the McCann et al U.S. Pat. No. 4,712,591, and the Holcomb et al U.S. Pat. No. 4,753,277. Automatic shut-off devices of this type have found considerable commercial acceptance in the last few years, and represent a signficant advance in the state of the art of automatic beverage dispensing.